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NLM uses a single record approach for material issued simultaneously in different formats, such as print, online and microfilm. This means that NLM creates one bibliographic record in LocatorPlus and the NLM Catalog which contains information about all the formats. NLM considers the single record approach to be less confusing to users, who will encounter fewer duplicate records. The holdings records indicate exactly which formats NLM owns and provide a URL hot link to the online version, if licensing agreements allow.
The primary description of the material is based on the first format received (most commonly print), with notes added about the other formats. In using the single record approach, NLM is not attempting to determine whether the print and online formats are identical, since the content of these formats can be mutable. The print and online formats may start out the same and later diverge, or conversely start out with different content and eventually become the same.
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http://www.nlm.nih.gov/services/cat_sor.html
Last reviewed: 10 August 2007
Last updated: 13 August 2007
First published: 10 August 2007
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